Geothermal Power Generation as Related to Resource Requirements

Abstract

For the past several years geothermal exploratory work has been conducted in northern Nevada. In conjunction with that effort a proposed 55-MW steam geothermal power plant was considered for initial installation in one of the fields being developed. The characteristics of the geothermal fields under consideration were not firm, with data indicating widely varying downhole temperatures. Thus, neither the resource nor the plant operating conditions could be set. To assist both the ultimate user of the resource, the utility, and the developer of the geothermal field, a series of parametric sensitivity studies were conducted for the initial evaluation of a field vis-a-vis the power plant. Using downhole temperature as the variable, the amount of brine, brine requirements/kWh, and pounds brine/pound of steam to the turbine were ascertained. This was done over a range of downhole temperatures of from 350F to 475F.

The studies illustrate the total interdependence of the geothermal resource and its associated power plant. The selection of geothermal steam power plant design conditions must be related to the field in which the plant is located. The results of the work have proven to be valuable in two major respects: (1) to determine the production required of a particular geothermal field to meet electrical generation output and (2) as field characteristics become firm, operating conditions can be defined for the associated power plant.